Analysing the internal electric field in GaN/InxGa1−xN MQW solar cells: A comparative study of Ga-face and N-face structures

Abstract

This study investigated the optical and electrical performance of Ga-face and N-face $\text{GaN}\left(p\right)-{\text{GaN}/\text{In}}_x{\text{Ga}}_{1-x}N\text{QW}-\text{GaN}\left(n\right)$ multiple quantum well solar cells (MQWSCs) to address the need for more efficient solar energy conversion. Using a numerical finite difference method (FDM), we analysed the impacts of built-in electric fields, spontaneous and piezoelectric polarizations, the quantum well (QW) size, the QW number, and the indium concentration on the optical and electrical characteristics of the proposed MQW solar cell. Our findings indicate that N-face structures align built-in and polarization fields, enhancing carrier generation and collection compared with Ga-face structures. Specifically, our results demonstrate that, at x = 0.6, w = 2 nm, and $N_{\text{QW}}=50$, the N-face structure achieves maximum conversion efficiencies of 26.56 % and 23.47 %, respectively, for the Ga-face structure. These findings demonstrate that tuning the QW thickness and indium concentration can optimize the MQWSC efficiency, with N-face structures achieving greater performance. This work highlights the potential of N-face p-i-n structures in advancing high-efficiency solar cells.